A model for physics-based fire simulation and analysis

Virtual Reality - This paper describes the development of a three-dimensional (3D) physics-based fire simulation model that employs the incompressible Navier–Stokes equations to realistically...     

飞机协同维修仿真的交互状态机模型

针对目前飞机维修场景众多的特点,提出一种适用于飞机协同维修的交互状态机模型。运用UML状态机建立维修人员、操作对象的状态转移模型,基于操作对象间的约束关系、操作对象-维修场景-维修人员的关系建立行为交互模型,将行为交互模型与状态转移模型融合,得到交互状态机模型,实现不同维修场景间的交互及状态变迁,给出模型的数学表达和图形化描述,使场景中实体对象的表达更加规范、统一,提高建模效率。以ADIRU排故为例,在分布式虚拟维修仿真平台上进行验证。     

A GIS-based urban simulation model for environmental health analysis

This paper introduces an urban simulation model for environmental health analysis (SIENA). SIENA is a novel tool to explore urban interactions and processes with regard to exposure assessments. It is based on urban structures and relationships observed in real-world cities making it a realistic representation of a functioning city. The development of SIENA involved identifying and quantifying fundamental processes and similarities in urban areas in Great Britain and using those to guide the building of SIENA within a GIS. An internal validation confirmed SIENA's realism. Its generality, achieved through the pooling of information from different real-world cities, makes it particularly useful for developing and testing spatial epidemiological concepts and models; simulating processes and interactions relating to environmental exposure; and exploring theoretical and methodological problems in the spatial analysis of environmental health. SIENA ultimately provides a much needed tool in the form of a controlled, simplified urban simulation model.     

A simulation model for risk analysis of toxic chemical storage

With the increasing complexity of chemical plants and the growing public concern for the safe manufacture, transport, and disposal of these chemicals, there exist a need to assist decision-makers in project evaluation with regard to risk.

Extensive work has been done in risk analysis area related to nuclear industry. The amount of research and applications of risk analysis methodology in chemical industry is seriously lacking. Direct application of some of the risk analysis techniques used for nuclear risk studies is not always appropriate to the chemical industry.

The use of simulation models to overcome some of the problems of direct application of probabilistic risk assessment (PRA) methodologies is evaluated in this paper. A simulation model is developed for a toxic chemical storage risk analysis problem. The results of the simulation model are compared to the results of using standard fault tree methodology.     

Comparative analysis for the G/G/R machine repair problem

Using approximate formulas for the probability density function of the number of failed machines in a G/G/R machine repair system obtained through diffusion approximation, a comparison between the approximate results with some of the exact existing results is made. The diffusion approximation approach is accurate enough for practical purposes and is a useful method for solving complex machine repair problems.     

Multi-server machine repair model with standbys and synchronous multiple vacation

This paper investigates a machine repair problem with homogeneous machines and standbys available, in which multiple technicians are responsible for supervising these machines and operate a (R, V, K) synchronous vacation policy. With such a policy, if any V idle technicians exist in the system, these V (V < R) technicians would take a synchronous vacation. Upon returning from vacation, they would take another vacation if there is no broken machine waiting in the queue. This pattern continues until at least one failed machine arrives. It is assumed that the number of teams/groups on vacation is less than or equal to K (0 ≦ KV < R). The matrix analytical method is employed to obtain a steady-state probability and the closed-form expression of the system performance measures. Efficient approaches are performed to deal with the optimization problem of the discrete/continuous variables while maintaining the system availability at a specified acceptable level.     

盾构机动态交互仿真系统的研究与实现

盾构机是用于开挖隧道等地下施工的专用工程机械,有着广阔的应用前 景。但因掘进装备等的高度复杂性,以及地质条件、工况的不确定性等导致的安全问题,对 盾构机的学习和研究带来一定难度。鉴于此,利用VRML、Cult3D、HTML 等开发了一个 基于网络的交互装配、运动仿真和虚拟漫游系统,具有导航漫游、交互操作虚拟对象、信息 查询等功能,形象直观地展示了盾构机的构造和原理,为盾构机的学习和研究提供了一个很 好的平台。     

关节臂式坐标测量机的虚拟样机模型及仿真

基于虚拟样机技术对六自由度关节臂式坐标测量机的测量空间进行研究和仿真,建立了六自由度关节臂式坐标测量机的测量运动学数学模型和虚拟样机模型。在建立起虚拟样机模型之后用图解法对其进行了检验,并将得到的虚拟样机模型与运动学数学模型进行比较验证,结果表明虚拟样机模型能够准确地反映测头位姿,方便有效地进行整个测量空间的运动仿真。正确的虚拟样机模型与测量运动学模型是研究测量机的误差空间分布的必要环节,为下一步工作奠定了研究基础。     

A network simulation model for police patrol vehicle maintenance and replacement analysis

Research in the field of urban police patrol-car analysis has tended to concentrate in the areas of vehicle deployment, fleetsize and location, etc., with very little emphasis in the area of vehicle maintenance and replacement policy. As such, the purpose of this paper is to develop and demonstrate a simulation model for patrol-vehicle replacement and maintenance analysis. The simulation model will encompass a Markov-type framework of state movements where the states represent the various stages of a patrol vehicle's life from new to inoperable. The model will be developed in the form of a Q-Gert network, and, demonstrated via a case example of an urban patrol fleet of 100 vehicles.     

基于后验概率SVM的仿真模型验证方法*

针对复杂系统建模与仿真中模型验证的特点,提出基于后验概率支持向量机（support vector machine, SVM）的仿真模型验证方法。采用基于误差分析的特征提取方法提取各可选仿真模型和实际系统输出的特征向量,利用各可选模型的特征向量及相应的模型标号组成训练集建立后验概率SVM模型,将实际系统的特征向量作用于后验概率SVM模型,依据其概率输出判别可选模型相对于实际系统的有效性。以某型飞行器制导控制系统仿真模型验证为例,证明了该方法的可行性和有效性。     

Sensitivity analysis of the machine repair problem with general repeated attempts

In this paper, we propose a machine repair problem with constant retrial policy, wherein if a failed machine finds the repairman busy upon arrival, it enters into an orbit. The machines in the orbit form a single waiting line, and only the one at the head of the orbit repeats its request for repair. The failure times of operating machines and the repair times of failed machines follow exponential distributions. It is assumed that retrial times are generally distributed. We used the supplementary variable technique to obtain explicit expressions for the steady-state probabilities of the number of failed machines in the orbit. We performed sensitivity analysis of the machine availability and operative efficiency with respect to system parameters and the number of machines in operation. The analysis of the busy period and the waiting time were also presented. Finally, we developed a cost model and formulated a cost minimization problem.     

Performance analysis of machine cell configurations using simulation

The objective of this research is to develop a generalized model that can analyze the performance of any cellular manufacturing system under various combinations of dispatching and loading policies. Early stages of the research along this line before generalization of the model is presented in this paper. A menu-driven SIMAN based simulation model is developed to analyze the performance of a particular cellular manufacturing system in terms of machine utilization, tool utilization, transporter (AGV) utilization, part waiting time, etc.     

Computational analysis of machine repair problem with unreliable multi-repairmen

This paper considers a multi-repairmen problem comprising of M operating machines with W warm standbys (spares). Both operating and warm standby machines are subject to failures. With a coverage probability c, a failed unit is immediately detected and attended by one of R repairmen if available. If the failed unit is not detected with probability 1−c, the system enters an unsafe state and must be cleared by a reboot action. The repairmen are also subject to failures which result in service (repair) interruptions. The failed repairman resumes service after a random period of time. In addition, the repair rate depends on number of failed machines. The entire system is modeled as a finite-state Markov chain and its steady state distribution is obtained by a recursive matrix approach. The major performance measures are evaluated based on this distribution. Under a cost structure, we propose to use the Quasi-Newton method and probabilistic global search Lausanne method to search for the global optimal system parameters. Numerical examples are presented to demonstrate the effectiveness of our approach in solving a highly complex manufacturing system subject to multiple uncertainties.     

Genetic algorithms for single machine scheduling with time-dependent deterioration and rate-modifying activities

In this paper, the integration of two emerging classes of scheduling problems, the class of scheduling problems with time-dependent deterioration and the class of scheduling problems with rate-modifying activities, are addressed. The scheduling problems have been studied independently. However, the integration of these classes is motivated by human operators of tasks who have fatigue while carrying out the operation of a series of tasks. This situation is also applicable to machines that experience performance degradation over time due to mal-position or mal-alignment of jobs, abrasion of tools, and scraps of operations, etc. It requires maintenance in order to sustain acceptable production rates. We consider the single machine scheduling problem with time-dependent deterioration and multiple RMAs. A mathematical model for an optimal solution to minimize the makespan is derived and genetic algorithms are proposed. The performance of the genetic algorithms is evaluated using randomly generated examples.     

实时图仿真中畸变模型的分析与建立

实时图的仿真生成是景像匹配仿真研究中的重要内容之一。系统研究了实时图仿真中的各种畸变模型的建立问题。分析了实时图与基准图之间存在的主要差异,设计了包括噪声干扰、几何畸变、灰度畸变等形式的十种畸变模型,给出了相应的实验结果。通过匹配仿真实验验证了这些模型在匹配算法性能评估及基准图可匹配性检验中的实用意义。     

A model of comparative stylistics for machine translation

The study of comparative stylistics attempts to catalogue and explain the differences in style between languages. Rules of comparative stylistics are commonly presented in textbooks of translation as simple rules of thumb, but if we hope to incorporate a knowledge of comparative stylistics into machine translation systems, we must take a more systematic approach. We develop a formal model of comparative syntactic stylistics to be used as a component of a general computational theory of style. We adapt textbook rules of human translation and study a small corpus of French-English translations to determine how these informal rules can be represented in our model as formal rules of translation. Our model of comparative stylistics could be implemented in a machine translation system, enabling the system to make a more informed decision about possible translation choices and their potential stylistic effects.     

Stochastic manufacturing system with process deterioration and machine breakdown

This paper presents a realistic manufacturing inventory model with process deterioration and machine breakdown. In economic manufacturing quantity model, process usually starts with ‘in-control’ state and produces items of good quality. After some random point of time, process may deteriorate and shift to ‘out-of-control’ state due to occurrence of assignable cause. From that point, process produces some percentage of non-conforming items. Further process deterioration after machine shift may result in machine breakdown at any random time during the production period. If machine breakdown occurs during the production period, then corrective (emergency) repair is performed immediately otherwise preventive (regular) repair is performed at the end of production period. The proposed model is formulated assuming that the time required for production facility shifting from ‘in-control’ state to ‘out-of-control’ state, time when machine breaks down, corrective and preventive repairing time and demand of items follows probability distribution. We have derived analytically the optimal production time which minimises the total expected production cost annually for machine breakdown and no machine breakdown cases. The solution procedure is illustrated with the help of numerical examples for different probability distributions. Sensitivity of the optimal solution with respect to different parameters are also analysed.     

A grid-based spatial data model for the simulation and analysis of individual behaviours in micro-spatial environments

As crowd simulation in micro-spatial environment is more widely applied in urban planning and management, the construction of an appropriate spatial data model that supports such applications becomes essential. To address the requirements necessary to building a model of crowd simulation and people–place relationship analysis in micro-spatial environments, the concept of the grid as a basic unit of people–place data association is presented in this article. Subsequently, a grid-based spatial data model is developed for modelling spatial data using Geographic Information System (GIS). The application of the model for crowd simulations in indoor and outdoor spatial environments is described. There are four advantages of this model: first, both the geometrical characteristics of geographic entities and behaviour characteristics of individuals within micro-spatial environments are involved; second, the object-oriented model and spatial topological relationships are fused; third, the integrated expression of indoor and outdoor environments can be realised; and fourth, crowd simulation models, such as Multi-agent System (MAS) and Cellular Automata (CA), can be further fused for intelligent simulation and the analysis of individual behaviours. Lastly, this article presents an experimental implementation of the data model, individual behaviours are simulated and analysed to illustrate the potential of the proposed model.     

A simplified model for the simulation and transformation of speech

This paper explores a model that reduces speech production to the specification of four time-varying parameters; F1 and F2, voice fundamental frequency (F₀), and a relative amplitude of the voice. The trajectory of the first two formants, F1 and F2, is treated as a series of coordinate pairs that are mapped from the F1F2 plane into a two-dimensional plane of coefficients. These coefficients are multipliers of two empirically-based orthogonal basis vectors which, when added to a neutral vowel area function, will produce a new area function with the desired locations of F1 and F2. Thus, area functions and voice parameters extracted at appropriate time intervals can be fed into a speech simulation model to recreate the original speech. A transformation of the speech can also be imposed by manipulating the area function and voice characteristics prior to the recreation of speech by simulation. The model has initially been developed for vowel-like speech utterances, but the effect of consonants on the F1F2 trajectory is also briefly addressed.